Finally, turning plastic pellets into 3D printer filament

Here’s the situation: a kilogram of 3D printer filament costs about $50. A kilogram of plastic pellets costs less than a tenth of that. Does anyone have a solution to this problem?

For years now, the general consensus was making your own 3D printer filament at home was nigh impossible, dealing with temperatures, pressures, and tolerances that home-built machines simply can’t handle. [Bradley] sent in a filament extruder he made because he was disturbed at this current mindset that desktop filament factories have huge technical issues that have yet to be overcome.

[Bradley]’s extruder is based on the Lyman Filament Extruder, a machine that has successfully demonstrated taking plastic pellets, forming them into a filament, and having this filament used in the production of 3D printed parts. [Bradley]’s improvements include a variable-speed motor, a larger hot end, and an automatic timing system to produce set quantities of printer filament.

Of course, since Inventables threw $40,000 at the problem of creating filament at home there were bound to be more than a few successful designs making their way out into the public. When we last covered the developments of home filament manufacturing, the Filabot seemed to be in the lead. Now with [Bradley] (and [Lyman])’s machines turning out usable filament, it’s only a matter of time before the 40 grand prize is snatched.

Not really – it’s more to do with economies of scale. There are large startup costs with doing a run on an industrial extruder, so you really have to make a lot of filament in a single go before the cost-per-length starts coming down.

Since the 3d printer market is still pretty small, few people were going to take the risk of a huge, expensive run just to be left with a large quantity of filament that they can’t sell.

Right – because any photo posted on this site should have all the working details obscured by protective covers. Just in case the photographer decided to reach a free hand into the mechanism while composing the photo.

Filament is only $50 if you don’t shop around.
I buy ABS for $14 kg and PLA for $15.
Even with postage to Australia I’m paying $25/kg.
repraper.com
I’m still waiting for my filabot but I doubt I’ll bother making filament I can buy cheap.
This machines will be great for trying blends we can’t buy.

The printer feeds filament in linearly, assuming that the filament has a constant volume per unit length. If the actual diameter varies, then the print will be inconsistent.
(It might have blobs hanging off where too much plastic was extruded, or voids where the filament was thinner than expected.)
Of course, if a printer could measure input volumetrically, uneven filament would be fine.
:)

It’s probably a stupid question, but why can’t 3d printers just use pellets instead of filament? I’m assuming the plastic they use never gets very flowable and the pellets would result in air gaps…or something.

The setup that turns the pellets into a steady stream for the 3D printer’s “head” is rather bulky, as you can see. So you don’t really want to mount it on a head that moves around the place (which is the leading mechanism). So now you have a pellet melter that feeds a stream of plastic to a mobile head a bit further. The larger that distance (determined by how far the head goes) the more difficult it gets to maintain a flow of heated plastic, it’ll cool. So you have the choice:
1. keep the plastic molten over a long-ish distance without a re-heater at the head. This is very cumbersome.
2. let the plastic cool and reheat it at the head.

To sum up: Having the plastic fed from pellets limits the distance the head can move and makes for a more complex setup.

The filabot people did it. I’m assuming the intermediate step is more economic in the end. You don’t want your print head heaving around a hopper full of plastic pellets and all the machinery to melt/compact them in a smaller printer.

On the filabot website, and more interesting to me, is the concept of using recyclable plastics instead of pellets. Just chop up Jr’s old toys and make new ones!

I used to work in a plastic pipe factory and they had a vacuum pump degassing the plastic where the plastic pellets first started to melt in the extruder….this was for PVC so I don’t know if it applies to this or not…thought it might be useful infomation …

Very cool, I enjoy the competition, but what do you mean “finally”? A month ago when you guys covered my extruder (over at projectspaghettidinner.wordpress.com or osprintingllc.com) we were making HDPE filament and weve been refining our tolerences (and adding more torque!) since then! I wouldnt call it “finally” I would call it “as well”. That said this is a sweet design, damn I love the 3D printing world

That price point is still tough to hit. I’ve said it before and I’ll say it again – it takes a lot of energy to extrude plastic and the more energy a machine consumes, the more expensive it’s going to be. The parts have to endure higher forces and temperatures and have some degree of precision.

The fact that there’s a $40k bounty tells me these guys already did the market research and if they can produce these machines in quantity for $250 each, they stand to make considerably more than $40,000. My advice to anyone who hits this price point – keep it to yourself and go into manufacturing. You’ll earn more than $40k.

What I am really wanting is one that you can just drop pet bottles into that will shred them then turn them into filament.

I have done a little molding using pet before and the temperature has to be pretty specific and cooling has to be slowed down a bit but if you could build a machine to make filament out of it you pretty much have free filament.

What about using a dual core wire
i.e. polycaprolactone/ABS in order
to mix it at the printhead?
Best of both worlds, essentially
a plastic “epoxy” that once
hardened becomes stronger than
both on their own.

As far as nylon weed trimmer filament being hygroscopic the treatment is the same as if you were using nylon pellet feed stock, you dry the feedstock before molding it. Conventional dryers used for dehydrating food would work for weed trimmer filament, in the injection molding industry hot air is pumped through hoses attached to the feed hopper so you dry the pellets on the fly. You need quite a bit of moisture to mess up an injection molded part from water vapor, so a simple trial and error approach with recording the drying time for each particular test batch of filament would render the correct time for the material. start at 100 to 120 degree F or check matweb.com for a generic nylon resin and use the reccomended dry times and temperature ranges to start with.

A meat grinder / sausage stuffer is all you really need to make your own filament. The main challenge is to get the heat away from the machine, but this can be easily done if you use a meat grinder attachment instead of an actual machine. The attachment will need to be mounted on a fixed base with a pulley or chain drive and a motor as picture above. A funnel shaped sausage stuffer attachment can be used to step down the flow from the meat grinders large opening. The end of the funnel will need to be fitted with the tube shaped heating element from an old coffee maker (be sure to descale it first), and the orifice will be somehow mounted to the heating element (by means of brass compression coupler with a cap on on other end. The cap gets drilled to the diameter of the filament (1.75 or 3.0mm). Heat can be applied to the meat grinder using stainless steal wire as an element and an electric control from an old electric stove to regulate the flow of power. A low voltage transformer can be used to maintain a low voltage and eliminate any risk of electrocution. Insulation of all the hot parts will require angel hair porcelain matting. And of course the filament gets dumped into a basin full of water made from an old 55 gallon drum. A motorized spool collects the filiament at the same rate it is fed by the auger.